Electric well heater



Sept. 21, 1965 c. I. WILLIAMS ELECTRIC WELL HEATER 2 Sheets-Sheet 1 Filed June 26. 1961 I N VEN TOR:

I. WILLIAMS R E T s E H C C. l. WILLIAMS ELECTRIC WELL HEATER Sept. 21, 1965 2 Sheets-Sheet 2 Filed June 26, 1961 I I r!!!!!!!!!!! ilv!!!!! IN V EN TOR.

CHESTER l. WLLIAMS BY United States Patent 3,207,220 ELECTRIC WELL HEATER Chester I. Williams, 347 Greenbriar SE., Grand Rapids, Mich. Filed June 26, 1961, Ser, No. 119,471 1 Claim. (Cl. 166-60) This invention relates to apparatus used in pumping operations in an oil well. In some geographical locations, the efiluent of an :oil well contains parafiin and other fractions which are congealable at the low temperatures commonly encountered in the winter season. As the mixed liquid is raised from the bearing formation to ground level, the temperature of it can easily undergo a very substantial drop. If this change is enough to bring the effiuent below the congealing point of any of its components, the solidified material will tend to clog the pipe and seriously interfere with pumping operations. This condition commonly becomes sufiiciently acute to require that pumping be shut down so that the solid accumulations can be physically pulled out. Time lost in the manner can easily amount to fifty percent in areas where the temperature and constituency conditions are present.

This invention eliminates the problem by maintaining the liquid state of the effluent by heating it, while it is still in the well, to a point above the congealing temperature. This is accomplished by the use of electric resistance-heating elements, preferably positioned between the inner and outer casings, or within the pump rod itself. Various types of circuits are provided, and a novel structural arrangement for supporting the heating elements is also included. In essence, the functioning of the present invention is to provide the addition of heat energy either to the well effiuent at a rate which will equal or exceed the heat loss to the surrounding cooler strata, or by providing a surrounding jacket of heat to establish a heated channel for the efiluent so that it will not become subject to an excessive temperature drop as it proceeds to the surface. The application of heat will preferably begin at a point below that at which the temperature of the surrounding formation approaches the first congealing point of the effluent mixture.

The reduction in viscosity accompanying the maintenance of elevated temperatures, together with the elimination of the throttling effect of congealed masses in the pipes, can reduce the pumping power enough to compensate for the input of heat. The cost of operating this invention may therefore work out to be small or even negative.

The several features of the invention will be analyzed in further detail through a discussion of the particular embodiments illustrated in the accompanying drawings, and from a discussion of the procedure involved in their utilization. In the drawings:

FIGURE 1 presents a sectional elevation adjacent the 'well head, and showing the installation of the heating elements.

FIGURE 2 presents a section on a plane perpendicular to the axis of the well bore adjacent the lower extremity of the heating elements.

FIGURE 3 illustrates a modified form of the invention, and presents a section through a hollow pump rod on a plane perpendicular to the axis thereof,

FIGURE 4 illustrates a recommended form of splice to connect successive sections of the heating element.

FIGURE 5 illustrates the cross-section of a preferred form of sheathed heating element.

FIGURE 6 presents a fragmentary view in perspective of the end of a terminal bolt for supporting the upper end of the heating element.

FIGURE 7 illustrates a modified form of the invention 3,207,220 Patented Sept. 21, 1965 "ice with regard to the heating element itself, for use in conjunction with an electric circuit which includes the liquid within the outer casing.

FIGURE 8 illustrates a further modification of the invention, in which the heating elements are positioned within the inner casing and are surrounded by the oil being pumped.

Referring to the drawings, FIGURE 1 illustrates a conventional well head structure, with the addition of equipment associated wtih the present invention. The upper end portion of the outer casing is indicated generally at 10, and a standard well head fitting is shown at 11. This unit provides the ports 12 and 13, and supports the wedge clamps 14 and 15 which grip the inner casing 16 securely according to conventional arrangements. The auxiliary fitting 17 is interposed between the outer casing 10 and the fitting 11 to accommodate the equipment used in conjunction with this invention. The fitting 17 is substantially annular, and has threaded engagement with the fitting 11 and the casing 10 as shown. The primary function of this new fitting is to provide for the support of the heating elements 18 which are interposed between the inner casing 16 and the outer casing 10. A plug 19, preferably of insulating material, is engaged with the side Wall of the fitting 17 with a standard system of pipe threads, and receives a bolt 20 which provides a cantilever support for the upper extremity of the heating elements 18. A major portion of the length of the bolt 20 is threaded for receiving the nuts 21 and 22, and the relative adjustment of these nuts along the length of the bolt will establish the radial distance of the heating elements 18 with respect to the axis of the inner and outer casings 16 and 10.

The end of the bolt 20 which supports the heating elements is best shown in FIGURE 6. A side-opening slot 23 is of sufiicient width to receive the heating element 18, and a counterbore 24 of a size to receive the nut 25 is preferably incorporated. Similarly, a second counterbore shown at 26 is provided on the underside of the bolt 20 for receiving the nut 27 The positioning of the nuts 25 and 27 can be selected to apply clamping action which will securely maintain the heating elements 18 in position. Once the nuts are properly adjusted, the presence of the counterbores 24 and 26 will further tend to maintain the assembled relationship.

The cross section of the heating element shown installed in FIGURE 1 is illustrated in detail in FIGURE 5. A core wire 28 having predetermined electrical resistance characteristics is surrounded by insulation as indicated at 29. A metallic sheath 30 serves the principal function of transferring the tension stresses resulting from the weight of long lengths of the heating element suspended from the end of the bolt 20. The thickness of the sheath 18 is preferably sufiicient to accept the threading for receiving the nuts 25 and 27.

The length of the resistance member 18 may be several hundreds of feet, and it will often be desirable to splice together succeeding sections to create such a length. An arrangement for a spliced joint with a heating element of the type shown in FIGURE 5 is shown in FIGURE 4. The element sections 31 and 32 are connected for transfer of tensile stresses by the splicing sleeve 33. This sleeve is slotted at the ends to provide axially-extending fingers 34 and 35, and the periphery of the fingers at each end is "provided with a tapered thread system such as a common pipe thread. The rings 36 and 37 have a similar thread incorporated on their internal surfaces, and tightening of these rings will result in constricting the fingers upon the sheathes of the heating elements 31 and 32. The gripping action may be facilitated by the incorporation of internal teeth as shown at 38 and 39. Prior to the installation of the tension-transferring sleeve 33, the core wires 40 and 41 are twisted together as shown at 42, and the exposed portion of the wires is covered by tape or other insulating filler as shown at 43.

The particular arrangement of the heating elements 18 to form a complete electrical circuit may be varied to suit the requirements of the particular installation. FIGURE 2 illustrates an arrangement in which four sections of heating element are arranged so that each provides a closed circuit. Each of the elements 18 includes a vertical section as shown at 44 and 45, which terminate at the upper ends as shown in FIGURE 1. These vertical sections are connected to form a U-shaped configuration by the portion 46 at the lower extremity of the heating element. At the upper end of each of the vertical sections, the core wire 28 is brought through an insulating plug 47 received in the fitting 17 with a system of pipe threads, the wire 28 extending to a point outside the fitting 17 to provide a terminal for the necessary connections to a source of voltage.

The modification illustrated in FIGURE 7 includes the core wire 48, the surrounding insulation 49, and the stresscarrying sheath 50. The significant point of difference of the modification shown in FIGURE 7 from that previously described is in the presence of the perforations 51 in the sheath and insulation to expose the core wire at these points. In situations involving saline solutions present between the inner and outer casings, the lower extremity of the heating element may be formed as shown in FIG- URE 7. This arrangement results in causing the electric current to proceed down the length of the heating element, and from there across to the casing through the saline solution at the points of contact provided by the perforations 51. The sheath and insulation serve to hold the core Wire away from direct contact with the casing to avoid grounding at a point farther up the element. If desired, the lower extremity of the core wire 28 may be brought into direct electrical contact with either of the casings by fully exposing a few inches of the wire and applying a lateral bend.

The modification shown in FIGURE 3 centers in the hollow pump rod indicated at 52. The tubular configuration of this rod provides a sufliciently thick wall to carry the stresses of the reciprocating pumping action, and still accommodates the heating elements 53 and 54 within the interior 55. The heating elements include the metallic conductors 56 and 57, respectively, and the insulation 58 and 59.

FIGURE 8 shows the installation of heating elements 60 and 61 within the inner casing 62 alongside the pump rod 63. These heating elements may be suspended from a fitting similar to the fitting 17 of FIGURE 1, but applied to the inner casing at a point above the well head 11. The adjustable mounting bolts would be set to position the heating elements close to the wall of the inner casing. There is some possibility that the reciprocating pump rod 63 might damage the heating elements, but this danger can be minimized by the application of suitable resilient rub rings 64 along the pump rod. At places Where the rod tends to drag on the inner casing as a result of axial misalignment, the cushioning effect of these rings will tend to gently displace the heating elements from a position of entrapment, causing them to seek a greater space toward the opposite side of the casing. The rings 64 may be applied to the heating elements, rather than to the rod. One advantage of the FIGURE 8 arrangement is the isolation of the heating elements from the saline solution 65 often found between the inner casing 62 and the outer casing 66. The electrolytic characteristics of saline solutions often cause problems of corrosion, and are diflicult to completely isolate from the core Wires wher it .is not desired to include the saline solution 65 in the electrical circuit. The oil well efiluent 67 within the inner casing is usually not so loaded with elec trolytic material as to present a serious problem.

The installation of the arrangements shown in FIG- URE 1 will normally take place prior to the application of the standard well head fitting 11. The space between the inner casing 16 and the outer casing 10 will be exposed as an annular opening down which sections of the heating element 18 may be lowered and progressively connected in series. When the desired length has been installed, the upper end is threaded to receive the nuts 25 and 27, which are held sufficiently spaced so that the element 18 can be slipped laterally into the slot 23 in the end of the bolt 20. When this has been accomplished, the weight of the device may be safely lowered onto the nut 25, with the nut 27 being tightened to provide the necessary clamping action. This same installation procedure would be applicable to the FIGURE 7 modification, and either type of heating element could have several sections joined together with the splicing unit shown in FIGURE 4 as the installation proceeds. When the FIGURE 3 modification is used, sections of the heating element would normally be incorporated in each of the interconnected sections of the pump rod, and the heating elements would be connected as the rod sections themselves are engaged. The insulated wires may be retained in place by auxiliary clamping devices (not shown) or may be adhesively secured. Since the connection of the successive lengths of the pump rod are normally accomplished by relative rota tion for engagement of threads, the connections of the heating elements (which must be made prior to the interengagement of the rod lengths) should necessarily be able to tolerate the amount of relative rotation necessary to engage the threads.

The particular embodiments of the present invention which have been illustrated and discussed herein are for illustrative purposes only and are not to be considered as a limitation upon the scope of the appended claim. In this claim, it is my intent to claim the entire invention disclosed herein, except as I am limited by the prior art.

I claim:

An oil wall structure, comprising: inner and outer casing means; and an electrical heating element disposed between said casing means, and including a conductor having insulated portions, and also having exposed portions said exposed and insulated portions alternating along the length of said heating element within the space between said casing means.

References Cited by the Examiner UNITED STATES PATENTS 1,309,721 7/19 Drinkern 166-60 1,457,479 6/ 23 Wolcott 166-60 X 1,732,617 10/29 Robinson 103-189 1,784,214 12/30 Workman 166-60 1,870,137 8/32 Parker 103-189 1,900,588 3/33 Scott 103-179 1,970,295 8/ 34 Fitzpatrick.

2,524,933 10/50 Silverman 166-4 2,597,261 5/52 Rhoads 166-60 X 2,608,256 8/52 Matthews 166-60 2,670,802 3/54 Ackley 166-60 X 2,754,912 7/56 Curson 166-60 2,781,851 2/57 Smith 166-60 2,975,721 3/61 Chancellor 103-179 2,994,377 8/ 61 Trantham 166-11 BENJAMIN HERSH, Primary Examiner.

CHARLES E. OCONNELL, Examiner. 

